We are very thankful to many friends and colleagues. Brian Downes, Jon Fisher, Blythe Janowiak, Laurie Russell, Laurie Shornick, Ranya Taqieddin, Kolin Clark, and Zisansha Zahirsha contributed to validation of the propositional accuracy rubric. Ranya Taqieddin also tested the rubrics used in this study, participating to establish interrater reliability. We thank Joe Dauer, Tammy Long, Jenni Momsen, Laurie Russell, and members of the Bray Speth lab for critically reviewing the manuscript and Lauren Arend for her advice on statistical analysis. This article is based on work supported in part by the National Science Foundation (NSF awards 0910278 and 1245410). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NSF.